ARM: dts: ux500: Totally separate TVK R2 and R3

There is no point in sharing any definitions between
the R2 and R3 versions of the TVK1281618 UIB. The
proximity sensor collides with the touchscreen etc,
it is less confusing to get rid of the overarching
TVK1281618 UIB file and just use one for each.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>